Space engineering - Thermal analysis handbook

This handbook is dedicated to the subject of thermal analysis for space applications. Thermal analysis is an important method of verification during the development of space systems. The purpose of this handbook is to provide thermal analysts with practical guidelines which support efficient and high quality thermal modelling and analysis.
Specifically, the handbook aims to improve:
1.the general comprehension of the context, drivers and constraints for thermal analysis campaigns;
2.the general quality of thermal models through the use of a consistent process for thermal modelling;
3.the credibility of thermal model predictions by rigorous verification of model results and outputs;
4.long term maintainability of thermal models via better model management, administration and documentation;
5.the efficiency of inter-organisation collaboration by setting out best practice for model transfer and conversion.
The intended users of the document are people, working in the domain of space systems, who use thermal analysis as part of their work. These users can be in industry, in (inter)national agencies, or in academia. Moreover, the guidelines are designed to be useful to users working on products at every level of a space project - that is to say at system level, sub-system level, unit level etc.
In some cases a guideline could not be globally applicable (for example not relevant for very high temperature applications). In these cases the limitations are explicitly given in the text of the handbook.

Raumfahrttechnik - Handbuch für thermische Analyse

Ingénierie spatiale - Manuel d'analyse thermique

Vesoljska tehnika - Priročnik o toplotni analizi

Ta priročnik je posvečen toplotni analizi za vesoljske tehnike. Toplotna analiza je pomembna metoda preverjanja pri razvoju vesoljskih sistemov. Namen tega priročnika je analitikom toplote zagotoviti praktične smernice, ki podpirajo učinkovito in visokokakovostno toplotno modeliranje oziroma analizo.
Natančneje, namen priročnika je izboljšati:
1. splošno razumevanje konteksta, ključnih dejavnikov in omejitev za izvedbo toplotne analize;
2. splošno kakovost toplotnih modelov z uporabo doslednega procesa toplotnega modeliranja;
3. verodostojnost napovedi toplotnega modela s strogim preverjanjem rezultatov in izhodnih podatkov modela;
4. dolgoročno vzdržljivost toplotnih modelov z boljšim upravljanjem, administracijo in dokumentacijo modelov;
5. učinkovitost medorganizacijskega sodelovanja z določitvijo dobre prakse za prenos in pretvorbo modelov.
Predvideni uporabniki dokumenta so osebe, ki delajo na področju vesoljskih sistemov in pri svojem delu uporabljajo toplotno analizo. To so lahko uporabniki v industriji, v (med)nacionalnih agencijah ali v akademskih krogih. Poleg tega so smernice zasnovane tako, da jih lahko uporabljajo tudi tisti, ki delajo na vseh ravneh vesoljskega projekta – to je na ravni sistema, ravni podsistema, ravni enote itd.
V nekaterih primerih smernice ni mogoče uporabiti globalno (na primer ni pomembna za uporabo pri zelo visokih temperaturah). V teh primerih so omejitve izrecno navedene v besedilu priročnika.

General Information

Status
Published
Public Enquiry End Date
27-Oct-2021
Publication Date
01-Feb-2022
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
31-Jan-2022
Due Date
07-Apr-2022
Completion Date
02-Feb-2022

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SLOVENSKI STANDARD
SIST-TP CEN/TR 17603-31-17:2022
01-marec-2022
Vesoljska tehnika - Priročnik o toplotni analizi
Space engineering - Thermal analysis handbook
Raumfahrttechnik - Handbuch für thermische Analyse
Ingénierie spatiale - Manuel d'analyse thermique
Ta slovenski standard je istoveten z: CEN/TR 17603-31-17:2022
ICS:
49.140 Vesoljski sistemi in operacije Space systems and
operations
SIST-TP CEN/TR 17603-31-17:2022 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST-TP CEN/TR 17603-31-17:2022
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SIST-TP CEN/TR 17603-31-17:2022
TECHNICAL REPORT CEN/TR 17603-31-17
RAPPORT TECHNIQUE
TECHNISCHER BERICHT
January 2022
ICS 49.140
English version
Space engineering - Thermal analysis handbook

Ingénierie spatiale - Manuel d'analyse thermique Raumfahrttechnik - Handbuch für thermische Analyse

This Technical Report was approved by CEN on 29 November 2021. It has been drawn up by the Technical Committee

CEN/CLC/JTC 5.

CEN and CENELEC members are the national standards bodies and national electrotechnical committees of Austria, Belgium,

Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy,

Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia,

Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom.
CEN-CENELEC Management Centre:
Rue de la Science 23, B-1040 Brussels
© 2022 CEN/CENELEC All rights of exploitation in any form and by any means
Ref. No. CEN/TR 17603-31-17:2022 E
reserved worldwide for CEN national Members and for
CENELEC Members.
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CEN/TR 17603-31-17:2022 (E)
Table of contents

European Foreword ................................................................................................... 6

1 Scope ....................................................................................................................... 7

1.1 Objectives and intended audience ............................................................................ 7

1.2 Context .....................................................................................................................7

2 References .............................................................................................................. 9

3 Terms, definitions and abbreviated terms .......................................................... 11

3.1 Terms from other documents .................................................................................. 11

3.2 Terms specific to the present document ................................................................. 12

3.3 Abbreviated terms................................................................................................... 13

4 Modelling guidelines ............................................................................................ 16

4.1 Model management ................................................................................................ 16

4.2 Model configuration and version control .................................................................. 17

4.3 Modelling process ................................................................................................... 17

4.4 Modularity and decomposition approach ................................................................. 19

4.5 Discretisation .......................................................................................................... 19

4.5.1 Overview ................................................................................................... 19

4.5.2 Spatial discretisation and mesh independence .......................................... 20

4.5.3 Observability ............................................................................................. 20

4.5.4 Time discretisation .................................................................................... 21

4.5.5 Input parameters ....................................................................................... 22

4.6 Transient analysis cases......................................................................................... 23

4.7 Modelling thermal radiation ..................................................................................... 23

4.7.1 Introduction to thermal radiation ................................................................ 23

4.7.2 Radiative environment .............................................................................. 24

4.7.3 Thermo-optical properties ......................................................................... 25

4.7.4 Transparency and optical elements ........................................................... 26

4.7.5 Spectral dependency ................................................................................ 26

4.7.6 Radiative cavities ...................................................................................... 27

4.7.7 Geometrical modelling .............................................................................. 28

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4.8 Considerations for non-vacuum environments ........................................................ 29

4.8.1 General ..................................................................................................... 29

4.8.2 Specific regimes ........................................................................................ 29

4.8.3 Conduction or convection .......................................................................... 29

4.8.4 Heat transfer coefficient correlation ........................................................... 30

4.8.5 Charge/discharge of gas inside pressurised systems ................................ 30

5 Model verification ................................................................................................. 31

5.1 Introduction to model verification ............................................................................ 31

5.2 Topology checks ..................................................................................................... 31

5.3 Steady state analysis .............................................................................................. 32

5.4 Finite element models ............................................................................................. 33

5.5 Verification of radiative computations...................................................................... 34

6 Uncertainty analysis ............................................................................................. 35

6.1 Uncertainty philosophy ........................................................................................... 35

6.2 Sources of uncertainties ......................................................................................... 36

6.2.1 General ..................................................................................................... 36

6.2.2 Environmental parameters ........................................................................ 36

6.2.3 Physical parameters .................................................................................. 37

6.2.4 Modelling parameters ................................................................................ 37

6.2.5 Test facility parameters ............................................................................. 37

6.3 Classical uncertainty analysis ................................................................................. 38

6.4 Stochastic uncertainty analysis ............................................................................... 39

6.5 Typical parameter inaccuracies .............................................................................. 39

6.6 Uncertainty analysis for heater controlled items ...................................................... 41

7 Model transfer, conversion and reduction ......................................................... 42

7.1 Model transfer ......................................................................................................... 42

7.1.1 Introduction to model transfer .................................................................... 42

7.1.2 Analysis files and reference results ........................................................... 42

7.1.3 Documentation .......................................................................................... 44

7.1.4 Portability of thermal models ..................................................................... 44

7.2 Model conversion.................................................................................................... 45

7.2.1 Introduction to model conversion ............................................................... 45

7.2.2 Management of thermal model conversions .............................................. 46

7.2.3 Model conversion workflow ....................................................................... 47

7.2.4 Verification of radiative model conversions ............................................... 50

7.2.5 Verification of thermal model (TMM) conversions ...................................... 52

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7.3 Model reduction ...................................................................................................... 52

7.3.1 Introduction to model reduction ................................................................. 52

7.3.2 Management ............................................................................................. 53

7.3.3 Model reduction guidelines ........................................................................ 53

7.3.4 Model reduction correlation success criteria .............................................. 54

7.3.5 Model reduction approaches ..................................................................... 55

Annex A Specific guidelines ................................................................................... 57

A.1 Multilayer insulation ................................................................................................ 57

A.1.1 Introduction ............................................................................................... 57

A.1.2 Modelling principles ................................................................................... 57

A.1.3 Modelling patterns ..................................................................................... 58

A.2 Heat pipes .............................................................................................................. 58

A.2.1 Introduction ............................................................................................... 58

A.2.2 Modelling principles ................................................................................... 59

A.2.3 Modelling patterns ..................................................................................... 59

A.2.4 Design verification ..................................................................................... 59

A.2.5 Model verification ...................................................................................... 60

A.3 Layered materials ................................................................................................... 60

A.3.1 Modelling principles ................................................................................... 60

A.3.2 Modelling patterns ..................................................................................... 60

A.4 Electronic units ....................................................................................................... 63

A.4.1 Introduction ............................................................................................... 63

A.4.2 Physical data and modelling advice .......................................................... 64

Figures

Figure 1-1: Thermal analysis in the context of a space project ............................................... 8

Figure 4-1: Modelling process .............................................................................................. 18

Figure 4-2: Examples of cavities: top showing two completely closed cavities, bottom

showing two almost separated cavities with a small opening .............................. 27

Figure 7-1: Diagram for the ideal model conversion workflow ............................................... 47

Figure 7-2: Activity diagram for conversion workflow - Conversion done by developer. ........ 48

Figure 7-3: Activity diagram for conversion workflow - Conversion done by recipient. .......... 48

Figure 7-4: Comparison of converted GMM radiative couplings ............................................ 51

: Typical heat pipe nodal topology ....................................................................... 59

: Example of verifying heat pipe heat transport capability .................................... 60

: Typical electronic unit thermal network ............................................................. 63

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Tables

Table 6-1: Typical parameter inaccuracies (pre-phase A and phase B) ................................ 39

Table 6-2: Typical parameter inaccuracies (phase B and phase C/D) .................................. 40

Table 7-1: Model reduction methods .................................................................................... 55

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European Foreword
This document (CEN/TR 17603-31-17:2022) has been prepared by Technical Committee
CEN/CLC/JTC 5 “Space”, the secretariat of which is held by DIN.

It is highlighted that this technical report does not contain any requirement but only collection of data

or descriptions and guidelines about how to organize and perform the work in support of EN16603-

31.

This Technical report (CEN/TR 17603-31-17:2022) originates from ECSS-E-HB-31-03A.

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CEN shall not be held responsible for identifying any or all such patent rights.

This document has been prepared under a mandate given to CEN by the European Commission and

the European Free Trade Association.

This document has been developed to cover specifically space systems and has therefore precedence

over any TR covering the same scope but with a wider domain of applicability (e.g.: aerospace).

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Scope
1.1 Objectives and intended audience

This handbook is dedicated to the subject of thermal analysis for space applications. Thermal analysis

is an important method of verification during the development of space systems. The purpose of this

handbook is to provide thermal analysts with practical guidelines which support efficient and high

quality thermal modelling and analysis.
Specifically, the handbook aims to improve:

a. the general comprehension of the context, drivers and constraints for thermal analysis

campaigns;

b. the general quality of thermal models through the use of a consistent process for thermal

modelling;

c. the credibility of thermal model predictions by rigorous verification of model results and

outputs;

d. long term maintainability of thermal models via better model management, administration and

documentation;

e. the efficiency of inter-organisation collaboration by setting out best practice for model transfer

and conversion.

The intended users of the document are people, working in the domain of space systems, who use

thermal analysis as part of their work. These users can be in industry, in (inter)national agencies, or in

academia. Moreover, the guidelines are designed to be useful to users working on products at every

level of a space project – that is to say at system level, sub-system level, unit level etc.

In some cases a guideline could not be globally applicable (for example not relevant for very high

temperature applications). In these cases the limitations are explicitly given in the text of the

handbook.
1.2 Context

The use of computational analysis to support the development of products is standard in modern

industry. Figure 1-1 illustrates the typical thermal modelling and analysis activities to be performed at

each phase of the development of a space system.
NOTE More information about the project lifecycle can be found in ECSS-
M-ST-10 [RD5].
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• Adapt thermal models for mission
• Analyse requirements
• Define final design of TCS • Perform mission predictions
• Define TCS concept
• Update thermal models (ground & flight)
• Perform trade-off
• Perform calculations covering all • Perform flight correlation
• Assess TRL of TCS
mission cases • Perform analysis in support of
products
operations
Phase B Phase C Phase D
Phase A Phase E
Preliminary Detailed Qualification
Feasibility Utilization
definition Definition production
PRR PDR CDR QR
• Adapt thermal models for test configuration
• Define preliminary design of TCS • Perform test prediction
• Develop thermal models • Perform test correlation

• Perform calculation for worst hot/cold • Update flight thermal models with outcomes

cases of test correlation

• Perform and correlate development tests • Perform analysis in support of production

activities
Figure 1-1: Thermal analysis in the context of a space project

It can be seen that thermal models are used during all phases of the space system development to

support a large number of activities, ranging from conceptual design right through to final in-flight

predictions.

Indeed, in some cases, thermal analysis is the only way that certain thermal requirements can be

verified; as physical tests are either too expensive or unrealisable. It is therefore vital for the credibility

of the predictions made that the quality of the models is as high as possible.
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References
RD # EN Reference Reference in text Title
[RD1] E N 16603-31 ECSS-E-ST-31, Space engineering - Thermal control general
requirements

[RD2] E N 16603-32-03 ECSS-E-ST-32-03 Space engineering - Structural finite element

models

[RD3] E N 16603-31-02 ECSS-E-ST-31-02 Space engineering - Two-phase heat transport

equipment

[RD4] T R 16603-31-01 ECSS-E-HB-31-01 Space engineering - Thermal design handbook

[RD5] E N-16601-10 ECSS-M-ST-10 Space project management - Project planning and
implementation
[RD6] E N 16601-00-01 ECSS-S-ST-00-01 ECSS system – Glossary of terms
[RD7] Gilmore, D., G., “Spacecraft Thermal Control
Handbook – Volume 1: Fundamental
Technologies”, 2002
[RD8] Anderson, B. J. and Smith, R. E. “Natural Orbital
Environment Guidelines for Use in Aerospace
Vehicle Development”, NASA Technical
Memorandum 4527, June 1994
[RD9] Anderson, B. J., Justus, C. G., and Batts, G. W.
“Guidelines for the Selection of Near-Earth
Thermal Environmental Parameters for Spacecraft
Design”, NASA Technical Memorandum 2001-
211221, October 2001
[RD10] Anderson, B. J., James, B. F., Justus, C. G., Batts
“Simple Thermal Environment Model (STEM)
User’s Guide, NASA Technical Memorandum
2001-211222, October 2001
[RD11] Sauer, A. “Implementation of the Equation of
Time in Sun Synchronous Orbit Modelling and
ESARAD Planet Temperature Mapping Error at
the Poles “, 22nd European Workshop on Thermal
and ECLS Software. October 2008.
https://exchange.esa.int/thermal-
workshop/attachments/workshop2008/
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RD # EN Reference Reference in text Title
[RD12] “Feasibility of Using a Stochastic Approach for
Space Thermal Analysis”, Blue Engineering &
Alenia Spazio, 2004,
https://exchange.esa.int/stochastic/
[RD13] “Guide for Verification and Validation in
Computational Solid Mechanics,” The American
Society of Mechanical Engineers, Revised Draft:
2006
[RD14] Remaury, S., Nabarra, P., Bellouard, E.,
d’Escrivan, S., “In-Flight Thermal Coatings
Ageing on the THERME Experiment” CNES,
Proceedings of the 9th International Symposium
on Materials in a Space Environment, 2003
Noordwijk, The Netherlands
[RD15] M. Molina & C. Clemente, “Thermal Model
Automatic Reduction: Algorithm and Validation
Techniques”, ICES 2006.
[RD16] F. Jouffroy, D. Charvet, M. Jacquiau and A.
Capitaine, “Automated Thermal Model Reduction
for Telecom S/C Walls”, 18th European Workshop
on Thermal and ECLS Software, 6–7 October 2004
[RD17] Gorlani M., Rossi M., “Thermal Model Reduction
with Stochastic Optimization”, 2007-01-3119, 37th
ICES Conference, 2007, Chicago
[RD18] M. Bernard, T. Basset, S. Leroy, F. Brunetti and J.
Etchells, “TMRT, a thermal model reduction tool”,
23rd European Workshop on Thermal and ECLS
Software, 6–7 October 2009
[RD19] STEP-TAS Technical Details
http://www.esa.int/TEC/Thermal_control/SEME7
NN0LYE_0.html
[RD20] CRTech, “How to Model a Heat Pipe”,
http://www.crtech.com/docs/papers/HowToMode
lHeatpipe.pdf
[RD21] Juhasz, A., “An Analysis and Procedure for
Determining Space Environmental Sink
Temperatures with Selected Computational
Results”, NASA Technical Memorandum 2001-
210063
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Terms, definitions and abbreviated terms
3.1 Terms from other documents

a. For the purpose of this document, the terms and definitions from ECSS-ST-00-01 [RD6] apply,

in particular for the following terms:
1. validation
NOTE Validation is the process of determining the degree to which a
computational model is an accurate representation of the real
world from the perspective of the intended uses of the model.
2. verification
NOTE 1 Verification is the process of determining that a computational
model accurately represents the underlying mathematical model
and its solution
NOTE 2 The topic of V&V is well known in the context of quality assurance
and systems engineering (including software systems). There has
also been some work in other domains such as Computational
Fluid Dynamics (CFD) and structural mechanics to develop
processes for V&V of simulation models. In the particular context
of computational analysis the formal definitions usually apply
[RD13].
NOTE 3 More informally the following questions are often used to explain
V&V in the context of computational analysis:
• Verification “did we solve the equations correctly?”
• Validation “did we solve the correct equations?”

b. For the purpose of this document, the terms and definitions from ECSS-E-ST-31 apply, in

particular for the following terms:
1. geometrical mathematical model

mathematical model in which an item and its surroundings are represented by radiation

exchanging surfaces characterised by their thermo-optical properties
2. thermal mathematical model

numerical representation of an item and its surroundings represented by concentrated

thermal capacitance nodes or elements, coupled by a network made of thermal
conductors (radiative, conductive and convective)
NOTE The current trend is towards integrated thermal modelling tools, in
which case the distinction between Geometrical Mathematical
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Model (GMM) and Thermal Mathematical Model (TMM) becomes
ill-defined. Nonetheless the terms GMM and TMM are still used in
the everyday language of thermal engineers and so the terms are
retained in this document.
3. thermal node

representation of a specific volume of an item with a representative temperature,

representative material properties and representative pressure (diffusion node) used in a

mathematical lumped parameter approach
NOTE The current document is written to be, as far as possible, tool and
method independent. It is therefore useful to generalise the
concept of thermal node to cover other numerical methods (e.g. the
finite element method). Mathematically speaking a thermal node
represents a “degree of freedom” in the equation system. More
practically, the purpose of a thermal node is to provide a
temperature evaluation (and output) at a selected location.
4. uncertainties

inaccuracies in temperature calculations due to inaccurate physical, environmental and

modelling parameters
NOTE This definition of uncertainty refers specifically to temperature
calculations. In the context of this document this is widened to
calculations of other key model outputs such as heater power or
duty cycle.
3.2 Terms specific to the present document
3.2.1 accuracy
degree of conformance between an output of a thermal analysis and the true value
NOTE The true value is usually a measurement from a physical test, for
example a thermal balance test. The purpose of the verification and
validation effort is thus to improve and quantify modelling
accuracy.
3.2.2 arithmetic thermal node
thermal node with zero thermal capacitance
NOTE 1 Arithmetic nodes are normally treated specially by thermal solvers
and a quasi-steady state solution is obtained for them during
transient runs. This is useful to avoid excessively small time steps
when lightweight items need to be represented in large models.
NOTE 2 Additionally arithmetic nodes are often used to represent thermal
interfaces or the edges of region
3.2.3 computational model
numerical implementation of a mathematical model
NOTE 1 This is usually comprises numerical discretisation, solution
algorithm, and convergence criteria.
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NOTE 2 This definition is taken from RD11, where a more detailed
discussion of the relationship between mathematical and
computation models can be found.
3.2.4 CSG
ratio of capacitance to sum of connected conductances for a thermal node
NOTE No specific acronym is available for CSG, most likely the C
represents capacitance, the S represents the sum, and the G
represents the conductors.
3.2.5 error

difference between an output of a thermal analysis and the true value

NOTE 1 High accuracy analyses therefore produce outputs with small
associated errors.
NOTE 2 This is a typical dictionary definition of error and generic. More
specific and formal definitions occur in a number of other sources,
for example ASME [RD13].
3.2.6 key model output(s)
output(s) from the thermal model having high level of importance
NOTE Examples of key model outputs are TRP temperatures, heater duty
cycles, and any other output form the model with special
significance for the verification of the TCS.
3.2.7 radiative cavity

collection of radiative surfaces of the thermal-radiative model, having the property that its surfaces

cannot exchange heat through thermal radiation with the surfaces belonging to another cavity

NOTE This term is synonymous with “radiative enclosure”.
3.2.8 radiative enclosure
See “radiative cavity”.
3.3 Abbreviated terms

For the purpose of this document, the abbreviated terms from ECSS-S-ST-00-01 and the following

apply:
Abbreviation Meaning
BOL beginning-of-life
CCHP constant conductance heat pipe
CFD computational fluid dynamics
CLA
coupled launcher analysis
CNES Centre National d'Etudes Spatiales
COTS commercial off-the-shelf
DGMM detailed geometrical mathematical model
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Abbreviation Meaning
DRD document requirements definition
DTMM detailed thermal mathematical model
EEE electrical, electronic and electromechanical
EOL
end-of-life
ESATAN
thermal/fluid analyser from ITP Engines
FEM finite element method
GMM geometrical mathematical model
HP heat pipe
HTC heat transfer coefficient
I/O
input / output
ICD
interface control document
ICES International Conference on Environmental Systems
IR infrared
KMO key model output(s)
LHP loop heat pipe
LP lumped parameter
MCRT
Monte Carlo ray tracing
MLI multi-layer insulation
OS open source
PCB printed circuit board
PID proportional integral derivative
PLM product lifecycle management
REF
radiation exchange factor
RGMM reduced geometrical mathematical model
RTMM reduced thermal mathematical model
S/C spacecraft
SDM simulation data management
SINDA thermal/fluid analyser from C&R technologies
SVD
singular value decomposition
thermal balance
TCS thermal control system
TMG thermal/fluid analyser from MAYA HTT Engineering Software Solutions
TMM thermal mathematical model
TMRT thermal model reduction tool
TRL
technology readiness level
TRP
temperature reference point
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...

SLOVENSKI STANDARD
kSIST-TP FprCEN/TR 17603-31-17:2021
01-oktober-2021
Vesoljska tehnika - Priročnik o toplotni analizi
Space engineering - Thermal analysis handbook
Raumfahrttechnik - Handbuch für thermische Analyse
Ingénierie spatiale - Manuel d'analyse thermique
Ta slovenski standard je istoveten z: FprCEN/TR 17603-31-17
ICS:
49.140 Vesoljski sistemi in operacije Space systems and
operations
kSIST-TP FprCEN/TR 17603-31-17:2021 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
kSIST-TP FprCEN/TR 17603-31-17:2021
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kSIST-TP FprCEN/TR 17603-31-17:2021
TECHNICAL REPORT
FINAL DRAFT
FprCEN/TR 17603-31-17
RAPPORT TECHNIQUE
TECHNISCHER BERICHT
August 2021
ICS 49.140
English version
Space engineering - Thermal analysis handbook

Ingénierie spatiale - Manuel d'analyse thermique Raumfahrttechnik - Handbuch für thermische Analyse

This draft Technical Report is submitted to CEN members for Vote. It has been drawn up by the Technical Committee

CEN/CLC/JTC 5.

CEN and CENELEC members are the national standards bodies and national electrotechnical committees of Austria, Belgium,

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Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom.

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Warning : This document is not a Technical Report. It is distributed for review and comments. It is subject to change without

notice and shall not be referred to as a Technical Report.
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© 2021 CEN/CENELEC All rights of exploitation in any form and by any means Ref. No. FprCEN/TR 17603-31-17:2021 E

reserved worldwide for CEN national Members and for
CENELEC Members.
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Table of contents

European Foreword ................................................................................................... 6

1 Scope ....................................................................................................................... 7

1.1 Objectives and intended audience ............................................................................ 7

1.2 Context ..................................................................................................................... 8

2 References .............................................................................................................. 9

3 Terms, definitions and abbreviated terms .......................................................... 11

3.1 Terms from other documents .................................................................................. 11

3.2 Terms specific to the present document ................................................................. 12

3.3 Abbreviated terms................................................................................................... 13

4 Modelling guidelines ............................................................................................ 15

4.1 Model management ................................................................................................ 15

4.2 Model configuration and version control .................................................................. 16

4.3 Modelling process ................................................................................................... 16

4.4 Modularity and decomposition approach ................................................................. 18

4.5 Discretisation .......................................................................................................... 18

4.5.1 Overview ................................................................................................... 18

4.5.2 Spatial discretisation and mesh independence .......................................... 19

4.5.3 Observability ............................................................................................. 19

4.5.4 Time discretisation .................................................................................... 20

4.5.5 Input parameters ....................................................................................... 21

4.6 Transient analysis cases......................................................................................... 22

4.7 Modelling thermal radiation ..................................................................................... 22

4.7.1 Introduction to thermal radiation ................................................................ 22

4.7.2 Radiative environment .............................................................................. 23

4.7.3 Thermo-optical properties ......................................................................... 24

4.7.4 Transparency and optical elements ........................................................... 25

4.7.5 Spectral dependency ................................................................................ 25

4.7.6 Radiative cavities ...................................................................................... 26

4.7.7 Geometrical modelling .............................................................................. 27

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4.8 Considerations for non-vacuum environments ........................................................ 28

4.8.1 General ..................................................................................................... 28

4.8.2 Specific regimes ........................................................................................ 28

4.8.3 Conduction or convection .......................................................................... 28

4.8.4 Heat transfer coefficient correlation ........................................................... 29

4.8.5 Charge/discharge of gas inside pressurised systems ................................ 29

5 Model verification ................................................................................................. 30

5.1 Introduction to model verification ............................................................................ 30

5.2 Topology checks ..................................................................................................... 30

5.3 Steady state analysis .............................................................................................. 31

5.4 Finite element models ............................................................................................. 32

5.5 Verification of radiative computations...................................................................... 33

6 Uncertainty analysis ............................................................................................. 34

6.1 Uncertainty philosophy ........................................................................................... 34

6.2 Sources of uncertainties ......................................................................................... 35

6.2.1 General ..................................................................................................... 35

6.2.2 Environmental parameters ........................................................................ 35

6.2.3 Physical parameters .................................................................................. 36

6.2.4 Modelling parameters ................................................................................ 36

6.2.5 Test facility parameters ............................................................................. 36

6.3 Classical uncertainty analysis ................................................................................. 37

6.4 Stochastic uncertainty analysis ............................................................................... 38

6.5 Typical parameter inaccuracies .............................................................................. 38

6.6 Uncertainty analysis for heater controlled items ...................................................... 40

7 Model transfer, conversion and reduction ......................................................... 41

7.1 Model transfer ......................................................................................................... 41

7.1.1 Introduction to model transfer .................................................................... 41

7.1.2 Analysis files and reference results ........................................................... 41

7.1.3 Documentation .......................................................................................... 43

7.1.4 Portability of thermal models ..................................................................... 43

7.2 Model conversion.................................................................................................... 44

7.2.1 Introduction to model conversion ............................................................... 44

7.2.2 Management of thermal model conversions .............................................. 45

7.2.3 Model conversion workflow ....................................................................... 46

7.2.4 Verification of radiative model conversions ............................................... 49

7.2.5 Verification of thermal model (TMM) conversions ...................................... 51

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7.3 Model reduction ...................................................................................................... 51

7.3.1 Introduction to model reduction ................................................................. 51

7.3.2 Management ............................................................................................. 52

7.3.3 Model reduction guidelines ........................................................................ 52

7.3.4 Model reduction correlation success criteria .............................................. 53

7.3.5 Model reduction approaches ..................................................................... 54

Annex A Specific guidelines ................................................................................... 56

A.1 Multilayer insulation ................................................................................................ 56

A.1.1 Introduction ............................................................................................... 56

A.1.2 Modelling principles ................................................................................... 56

A.1.3 Modelling patterns ..................................................................................... 57

A.2 Heat pipes .............................................................................................................. 57

A.2.1 Introduction ............................................................................................... 57

A.2.2 Modelling principles ................................................................................... 58

A.2.3 Modelling patterns ..................................................................................... 58

A.2.4 Design verification ..................................................................................... 58

A.2.5 Model verification ...................................................................................... 59

A.3 Layered materials ................................................................................................... 59

A.3.1 Modelling principles ................................................................................... 59

A.3.2 Modelling patterns ..................................................................................... 59

A.4 Electronic units ....................................................................................................... 62

A.4.1 Introduction ............................................................................................... 62

A.4.2 Physical data and modelling advice .......................................................... 63

Figures

Figure 1-1: Thermal analysis in the context of a space project ............................................... 8

Figure 4-1: Modelling process .............................................................................................. 17

Figure 4-2: Examples of cavities: top showing two completely closed cavities, bottom

showing two almost separated cavities with a small opening .............................. 26

Figure 7-1: Diagram for the ideal model conversion workflow ............................................... 46

Figure 7-2: Activity diagram for conversion workflow - Conversion done by developer. ........ 47

Figure 7-3: Activity diagram for conversion workflow - Conversion done by recipient. .......... 47

Figure 7-4: Comparison of converted GMM radiative couplings ............................................ 50

Figure A-1 : Typical heat pipe nodal topology ....................................................................... 58

Figure A-2 : Example of verifying heat pipe heat transport capability .................................... 59

Figure A-3 : Typical electronic unit thermal network ............................................................. 62

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Tables

Table 6-1: Typical parameter inaccuracies (pre-phase A and phase B) ................................ 38

Table 6-2: Typical parameter inaccuracies (phase B and phase C/D) .................................. 39

Table 7-1: Model reduction methods .................................................................................... 54

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European Foreword

This document (FprCEN/TR 17603-31-17:2021) has been prepared by Technical Committee

CEN/CLC/JTC 5 “Space”, the secretariat of which is held by DIN.

It is highlighted that this technical report does not contain any requirement but only collection of data

or descriptions and guidelines about how to organize and perform the work in support of EN16603-

31.

This Technical report (FprCEN/TR 17603-31-17:2021) originates from ECSS-E-HB-31-03A.

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such

patent rights.

This document has been prepared under a mandate given to CEN by the European Commission and

the European Free Trade Association.

This document has been developed to cover specifically space systems and has therefore precedence

over any TR covering the same scope but with a wider domain of applicability (e.g.: aerospace).

This document is currently submitted to the CEN CONSULTATION.
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Scope
1.1 Objectives and intended audience

This handbook is dedicated to the subject of thermal analysis for space applications. Thermal analysis

is an important method of verification during the development of space systems. The purpose of this

handbook is to provide thermal analysts with practical guidelines which support efficient and high

quality thermal modelling and analysis.
Specifically, the handbook aims to improve:

a. the general comprehension of the context, drivers and constraints for thermal analysis

campaigns;

b. the general quality of thermal models through the use of a consistent process for thermal

modelling;

c. the credibility of thermal model predictions by rigorous verification of model results and

outputs;

d. long term maintainability of thermal models via better model management, administration and

documentation;

e. the efficiency of inter-organisation collaboration by setting out best practice for model transfer

and conversion.

The intended users of the document are people, working in the domain of space systems, who use

thermal analysis as part of their work. These users can be in industry, in (inter)national agencies, or in

academia. Moreover, the guidelines are designed to be useful to users working on products at every

level of a space project – that is to say at system level, sub-system level, unit level etc.

In some cases a guideline could not be globally applicable (for example not relevant for very high

temperature applications). In these cases the limitations are explicitly given in the text of the

handbook.
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1.2 Context

The use of computational analysis to support the development of products is standard in modern

industry. Figure 1-1 illustrates the typical thermal modelling and analysis activities to be performed at

each phase of the development of a space system.
NOTE More information about the project lifecycle can be found in ECSS‐
M‐ST‐10 [RD5].
· Adapt thermal models for mission
· Analyse requirements
· Define final design of TCS · Perform mission predictions
· Define TCS concept
· Update thermal models (ground & flight)
· Perform trade-off
· Perform calculations covering all · Perform flight correlation
· Assess TRL of TCS
mission cases · Perform analysis in support of
products
operations
Phase B Phase C Phase D
Phase A Phase E
Preliminary Detailed Qualification
Feasibility Utilization
definition Definition production
PRR PDR CDR QR
· Adapt thermal models for test configuration
· Define preliminary design of TCS · Perform test prediction
· Develop thermal models · Perform test correlation

· Perform calculation for worst hot/cold · Update flight thermal models with outcomes

cases of test correlation

· Perform and correlate development tests · Perform analysis in support of production

activities
Figure 1-1: Thermal analysis in the context of a space project

It can be seen that thermal models are used during all phases of the space system development to

support a large number of activities, ranging from conceptual design right through to final in-flight

predictions.

Indeed, in some cases, thermal analysis is the only way that certain thermal requirements can be

verified; as physical tests are either too expensive or unrealisable. It is therefore vital for the credibility

of the predictions made that the quality of the models is as high as possible.
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References
RD # EN Reference Reference in text Title
[RD1] E N 16603-31 ECSS-E-ST-31, Space engineering - Thermal control general
requirements

[RD2] E N 16603-32-03 ECSS-E-ST-32-03 Space engineering - Structural finite element

models

[RD3] E N 16603-31-02 ECSS-E-ST-31-02 Space engineering - Two-phase heat transport

equipment

[RD4] TR 16603-31-01 ECSS-E-HB-31-01 Space engineering - Thermal design handbook

[RD5] EN -16601-10 ECSS-M-ST-10 Space project management - Project planning and
implementation
[RD6] E N 16601-00-01 ECSS-S-ST-00-01 ECSS system – Glossary of terms
[RD7] Gilmore, D., G., “Spacecraft Thermal Control
Handbook – Volume 1: Fundamental
Technologies”, 2002
[RD8] Anderson, B. J. and Smith, R. E. “Natural Orbital
Environment Guidelines for Use in Aerospace
Vehicle Development”, NASA Technical
Memorandum 4527, June 1994
[RD9] Anderson, B. J., Justus, C. G., and Batts, G. W.
“Guidelines for the Selection of Near-Earth
Thermal Environmental Parameters for Spacecraft
Design”, NASA Technical Memorandum 2001-
211221, October 2001
[RD10] Anderson, B. J., James, B. F., Justus, C. G., Batts
“Simple Thermal Environment Model (STEM)
User’s Guide, NASA Technical Memorandum
2001-211222, October 2001
[RD11] Sauer, A. “Implementation of the Equation of
Time in Sun Synchronous Orbit Modelling and
ESARAD Planet Temperature Mapping Error at
the Poles “, 22nd European Workshop on Thermal
and ECLS Software. October 2008.
https://exchange.esa.int/thermal-
workshop/attachments/workshop2008/
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RD # EN Reference Reference in text Title
[RD12] “Feasibility of Using a Stochastic Approach for
Space Thermal Analysis”, Blue Engineering &
Alenia Spazio, 2004,
https://exchange.esa.int/stochastic/
[RD13] “Guide for Verification and Validation in
Computational Solid Mechanics,” The American
Society of Mechanical Engineers, Revised Draft:
2006
[RD14] Remaury, S., Nabarra, P., Bellouard, E.,
d’Escrivan, S., “In-Flight Thermal Coatings
Ageing on the THERME Experiment” CNES,
Proceedings of the 9th International Symposium
on Materials in a Space Environment, 2003
Noordwijk, The Netherlands
[RD15] M. Molina & C. Clemente, “Thermal Model
Automatic Reduction: Algorithm and Validation
Techniques”, ICES 2006.
[RD16] F. Jouffroy, D. Charvet, M. Jacquiau and A.
Capitaine, “Automated Thermal Model Reduction
for Telecom S/C Walls”, 18th European Workshop
on Thermal and ECLS Software, 6–7 October 2004
[RD17] Gorlani M., Rossi M., “Thermal Model Reduction
with Stochastic Optimization”, 2007-01-3119, 37th
ICES Conference, 2007, Chicago
[RD18] M. Bernard, T. Basset, S. Leroy, F. Brunetti and J.
Etchells, “TMRT, a thermal model reduction tool”,
23rd European Workshop on Thermal and ECLS
Software, 6–7 October 2009
[RD19] STEP-TAS Technical Details
http://www.esa.int/TEC/Thermal_control/SEME7
NN0LYE_0.html
[RD20] CRTech, “How to Model a Heat Pipe”,
http://www.crtech.com/docs/papers/HowToMode
lHeatpipe.pdf
[RD21] Juhasz, A., “An Analysis and Procedure for
Determining Space Environmental Sink
Temperatures with Selected Computational
Results”, NASA Technical Memorandum 2001-
210063
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Terms, definitions and abbreviated terms
3.1 Terms from other documents

a. For the purpose of this document, the terms and definitions from ECSS‐ST‐00‐01 [RD6] apply,

in particular for the following terms:
1. validation
NOTE Validation is the process of determining the degree to which a
computational model is an accurate representation of the real
world from the perspective of the intended uses of the model.
2. verification
NOTE 1 Verification is the process of determining that a computational
model accurately represents the underlying mathematical model
and its solution
NOTE 2 The topic of V&V is well known in the context of quality assurance
and systems engineering (including software systems). There has
also been some work in other domains such as Computational
Fluid Dynamics (CFD) and structural mechanics to develop
processes for V&V of simulation models. In the particular context
of computational analysis the formal definitions usually apply
[RD13].
NOTE 3 More informally the following questions are often used to explain
V&V in the context of computational analysis:
· Verification “did we solve the equations correctly?”
· Validation “did we solve the correct equations?”

b. For the purpose of this document, the terms and definitions from ECSS‐E‐ST‐31 apply, in

particular for the following terms:
1. geometrical mathematical model

mathematical model in which an item and its surroundings are represented by radiation

exchanging surfaces characterised by their thermo‐optical properties
2. thermal mathematical model

numerical representation of an item and its surroundings represented by concentrated

thermal capacitance nodes or elements, coupled by a network made of thermal
conductors (radiative, conductive and convective)
NOTE The current trend is towards integrated thermal modelling tools, in
which case the distinction between Geometrical Mathematical
Model (GMM) and Thermal Mathematical Model (TMM) becomes
ill-defined. Nonetheless the terms GMM and TMM are still used in
the everyday language of thermal engineers and so the terms are
retained in this document.
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3. thermal node

representation of a specific volume of an item with a representative temperature,

representative material properties and representative pressure (diffusion node) used in a

mathematical lumped parameter approach
NOTE The current document is written to be, as far as possible, tool and
method independent. It is therefore useful to generalise the
concept of thermal node to cover other numerical methods (e.g. the
finite element method). Mathematically speaking a thermal node
represents a “degree of freedom” in the equation system. More
practically, the purpose of a thermal node is to provide a
temperature evaluation (and output) at a selected location.
4. uncertainties

inaccuracies in temperature calculations due to inaccurate physical, environmental and

modelling parameters
NOTE This definition of uncertainty refers specifically to temperature
calculations. In the context of this document this is widened to
calculations of other key model outputs such as heater power or
duty cycle.
3.2 Terms specific to the present document
3.2.1 accuracy
degree of conformance between an output of a thermal analysis and the true value
NOTE The true value is usually a measurement from a physical test, for
example a thermal balance test. The purpose of the verification and
validation effort is thus to improve and quantify modelling
accuracy.
3.2.2 arithmetic thermal node
thermal node with zero thermal capacitance
NOTE 1 Arithmetic nodes are normally treated specially by thermal solvers
and a quasi-steady state solution is obtained for them during
transient runs. This is useful to avoid excessively small time steps
when lightweight items need to be represented in large models.
NOTE 2 Additionally arithmetic nodes are often used to represent thermal
interfaces or the edges of region
3.2.3 computational model
numerical implementation of a mathematical model
NOTE 1 This is usually comprises numerical discretisation, solution
algorithm, and convergence criteria.
NOTE 2 This definition is taken from RD11, where a more detailed
discussion of the relationship between mathematical and
computation models can be found.
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3.2.4 CSG
ratio of capacitance to sum of connected conductances for a thermal node
NOTE No specific acronym is available for CSG, most likely the C
represents capacitance, the S represents the sum, and the G
represents the conductors.
3.2.5 error

difference between an output of a thermal analysis and the true value

NOTE 1 High accuracy analyses therefore produce outputs with small
associated errors.
NOTE 2 This is a typical dictionary definition of error and generic. More
specific and formal definitions occur in a number of other sources,
for example ASME [RD13].
3.2.6 key model output(s)
output(s) from the thermal model having high level of importance
NOTE Examples of key model outputs are TRP temperatures, heater duty
cycles, and any other output form the model with special
significance for the verification of the TCS.
3.2.7 radiative cavity

collection of radiative surfaces of the thermal-radiative model, having the property that its surfaces

cannot exchange heat through thermal radiation with the surfaces belonging to another cavity

NOTE This term is synonymous with “radiative enclosure”.
3.2.8 radiative enclosure
See “radiative cavity”.
3.3 Abbreviated terms

For the purpose of this document, the abbreviated terms from ECSS-S-ST-00-01 and the following

apply:
Abbreviation Meaning
BOL beginning-of-life
CCHP
constant conductance heat pipe
CFD computational fluid dynamics
CLA coupled launcher analysis
CNES Centre National d'Etudes Spatiales
COTS commercial off-the-shelf
DGMM detailed geometrical mathematical model
DRD
document requirements definition
DTMM detailed thermal mathematical model
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Abbreviation Meaning
EEE electrical, electronic and electromechanical
EOL end-of-life
ESATAN thermal/fluid analyser from ITP Engines
FEM
finite element method
GMM
geometrical mathematical model
HP heat pipe
HTC heat transfer coefficient
I/O input / output
ICD interface control document
ICES International Conference on Environmental Systems
infrared
KMO key model output(s)
LHP loop heat pipe
LP lumped parameter
MCRT Monte Carlo ray tracing
MLI multi-layer insulation
open source
PCB
printed circuit board
PID proportional integral der
...

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